The present invention relates to cold-water-dispersible, modified starches characterized by their instant gelling properties and to a process for their preparation. It also relates to food systems containing such starches.
It is often desirable to prepare food systems which have a set or gel texture, such as pie fillings, puddings and jellies. Many of these food systems containing gelling agents which must be cooked to effect gelation. Such gelling agents include agar, gelatin, corn starch, pectin, carrageenin, algin, and combinations of locust-bean gum and xanthan gum. In addition, starches derived from, e.g., corn, potato, tapioca, and wheat which are acid-converted to a certain water fluidity level will retrograde to a gel when cooked.
An example of a food product which requires cooking to effect gelation is the conventional starch-based pudding, which generally consists of an ungelatinized starch, flavorings, sweetening agents, etc. Such puddings are prepared for consumption by adding milk, cooking until the starch is gelatinized, pouring the cooked mixture into a bowl or individual serving dishes, and cooling and/or refrigerating.
There are, however, certain disadvantages associated with food systems of this type. In addition to the fact that cooking of the food system is necessary to impart the gel texture thereto, many of the gelling agents used in these systems require specific conditions. Thus, for example, gelation can be used only after dissolution in very hot water, and typical pectins for use in jellies require about 65% sugar solids to produce a gel.
There are food systems which have a set or gel texture which forms without cooking. Most of these products are milk-based and consist of pregelatinized (i.e., cold-water dispersible) starch, one or more setting agents, which are usually phosphate salts (e.g., tetrasodium pyrophosphate), and flavoring, sweetening, and coloring agents. The set or gel properties of these food systems are obtained from the interaction of the phosphate salts with the casein and calcium ion provided by the milk, and not with the starch ingredient in the formulation. The pregelatinized starch functions as a viscosity builder or thickening agent, but is not the prime factor in the development of the gel structure of the prepared food system.
The major drawback of these uncooked, so-called "instant", food systems it that they do not have the firm gel structure of the cooked systems, i.e., they do not cut as cleanly with a spoon; and their texture, rather than being smooth, is generally described as "grainy" in both appearance and "mouth-feel" characteristics. Moreover, the setting salts are not operative at low pH or in non-milk-based food systems.
U.S. Pat. No. 3,583,874 issued June 8, 1971 to F. Germino et al. discloses a starch composition suitable as gelling agent in instant puddings, which comprises a blend of pregelatinized, defatted starch and a granular, preswollen starch having a water fluidity in a certain range.
The process disclosed in U.S. Pat. No. 4,207,355 issued June 10, 1980 to C.-W. Chiu et al. to produce a cold-water-dispersible, modified tapioca starch which has instant gelling properties consists of converting the starch to a certain water fluidity, crosslinking the starch, and then drum drying the converted, crosslinked starch. The reverse process is described in U.S. Pat. No. 4,229,489 issued Oct. 21, 1980 to C.-W. Chiu et al. Further, U.S. Pat. No. 4,228,199 issued Oct. 14, 1980 to C.-W. Chiu et al. discloses a cold-water-dispersible potato starch prepared by drum drying a crosslinked, and optionally fluidized (i.e. converted) starch.
In some applications, however, chemically altered starches are undesirable or unacceptable, as in certain food uses, and efforts are being made to prepare non-chemically modified starches, i.e. starches that do not have substituents introduced through covalent linkages. The prior art methods for producing non-chemically modified starches involved heat-moisture treatments that have resulted in inhibited starches having properties similar to those of chemically crosslinked starches, but these treatments have not produced instant gelling starches.
One such treatment is described by L. Sair in "Methods in Carbohydrate Chemistry,", Vol IV (Starch), pp. 283-285, R. L. Whistler, ed. (Academic Press, New York 1964). The treatment changes the sorption properties of the starch with corresponding changes in gelatinization temperature, translucency, and pasting characteristics. It is carried out by heating the starch in a pressure cooker at 100% relative humidity for from 2-18 hr. at 95.degree. C. or for up to 16 hr. at 100.degree.-110.degree. C. The treatment can also be carried out in an air oven after adjusting the starch's moisture content to about 18-27%. The resulting starches are not pregelatinized (i.e., instant) nor are they gelling. The potato starch may, after subsequent cooking to gelatinize it, show some gelling properties.
Another heat-moisture treatment is described in U.S. Pat. No. 3,977,897 issued Aug. 31, 1976 to O. B. Wurzburg et al. It is carried out by the controlled heating at a specified pH of an aqueous suspension containing an amylose-containing starch in intact granule form and selected inorganic salts which are effective in raising the gelatinization temperature of the starch. The resulting starch is neither pregelatinized nor gelling.
The heat-moisture treatment disclosed in U.S. Pat. No. 4,013,799 issued Mar. 22, 1977 to W. J. Smalligan et al. is likewise carried out under conditions that are such that the tapioca starch does not gelatinize, nor is it gelling. The treatment is carried out by heating granular tapioca starch having a moisture content of about 15-35% for 1-72 hours at 70.degree.-130.degree. C.
The present invention provides an instant gelling tapioca starch or potato starch which forms at least a weak gel when dispersed in cold water (i.e., without cooking) and which is useful in low pH, as well as in high pH, food systems. In the preferred embodiment, the instant gelling starches are prepared without conversion or other chemical modification. A food system containing the instant gelling starches is also provided.